wip: OpenGraph support

Author: SolarLiner

contrib/opengraph/__init__.py

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+from django.apps import AppConfig
+
+
+class OpengraphConfig(AppConfig):
+    app_name = "opengraph"

contrib/opengraph/apps.py

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+from pathlib import Path
+
+from PIL import Image, ImageDraw, ImageFont
+
+OGRAPH_SIZE = (1200, 630)
+DATADIR = Path(__file__).parent / "data"
+LOGO = DATADIR / "logo.png"
+GRADIENT = DATADIR / "gradient.png"
+FONT = DATADIR / "fonts" / "WorkSans-Medium.ttf"
+
+
+def center(canvas: tuple[int, int], size: tuple[int, int]) -> tuple[int, int, int, int]:
+    cw, ch = canvas
+    w, h = size
+    assert cw >= w and ch >= h
+
+    mw = cw - w
+    mh = ch - h
+    x = mw / 2
+    y = mh / 2
+    return int(x), int(y), w, h
+
+
+def resize_fill(im: Image.Image, size: tuple[int, int]) -> Image.Image:
+    w, h = size
+    sw, sh = im.size
+    ratio = max(w / sw, h / sh)
+    new_size = (int(sw * ratio), int(sh * ratio))
+
+    box = center(new_size, size)
+
+    print("box", box, "new_size", new_size)
+    return im.resize(new_size)  # .crop(box)
+
+
+def layout_lines(font: ImageFont.FreeTypeFont, title: str, bounds: tuple[int, int]) -> Image.Image:
+    lines: list[str] = []
+    for line in title.splitlines():
+        cur_line = ""
+        for word in line.split():
+            if font.getsize(cur_line)[0] > bounds[0]:
+                lines.append(cur_line)
+                cur_line = ""
+            cur_line += f"{word} "
+            cur_line.strip()
+        if len(cur_line) > 0:
+            lines.append(cur_line.strip())
+
+    text = "\n".join(lines)
+    fw, fh = font.getsize_multiline(text)
+    size = (fw, max(fh, bounds[1]))
+    im = Image.new("RGBA", size)
+    draw = ImageDraw.Draw(im)
+    draw.multiline_text((0, 0), text, font=font)
+    return im
+
+
+def assemble(bg: Image.Image, title: str) -> Image.Image:
+    out = Image.new("RGBA", OGRAPH_SIZE, "black")
+    out.paste(resize_fill(bg, OGRAPH_SIZE))
+    with Image.open(str(LOGO)) as logo:
+        out.alpha_composite(logo)
+    with Image.open(str(GRADIENT)) as gradient:
+        y = OGRAPH_SIZE[1] - gradient.size[1]
+        out.alpha_composite(gradient, (0, y))
+
+    font = ImageFont.truetype(str(FONT), 40)
+    margin = 60
+    tw = OGRAPH_SIZE[0] - 2 * margin
+    text_layer = layout_lines(font, title, (tw, 400))
+    ty = OGRAPH_SIZE[1] - margin - text_layer.size[1]
+    print("Text layer:", (margin, ty), text_layer.size)
+    out.alpha_composite(text_layer, (margin, ty))
+
+    return out

contrib/opengraph/data/fonts/WorkSans-Medium.ttf

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+# Generated by Django 2.2.18 on 2021-09-16 16:33
+
+import contrib.opengraph.models
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ('wagtailcore', '0060_fix_workflow_unique_constraint'),
+        ('wagtailimages', '0023_add_choose_permissions'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='OpenGraphRendition',
+            fields=[
+                ('key', models.CharField(max_length=256, primary_key=True, serialize=False)),
+                ('rendered', models.ImageField(height_field='height', upload_to=contrib.opengraph.models.upload_og_image, width_field='width')),
+                ('width', models.IntegerField()),
+                ('height', models.IntegerField()),
+            ],
+        ),
+        migrations.CreateModel(
+            name='OpenGraphSettings',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('default_subtitle', models.CharField(max_length=80, verbose_name='Sous-titre par défaut')),
+                ('default_bg_image', models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='+', to='wagtailimages.Image')),
+                ('site', models.OneToOneField(editable=False, on_delete=django.db.models.deletion.CASCADE, to='wagtailcore.Site')),
+            ],
+            options={
+                'verbose_name': 'paramètres OpenGraph',
+                'verbose_name_plural': 'paramètres OpenGraph',
+            },
+        ),
+    ]

contrib/opengraph/data/gradient.png

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+# Generated by Django 2.2.18 on 2021-09-16 16:42
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('opengraph', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='opengraphsettings',
+            name='default_subtitle',
+        ),
+    ]

contrib/opengraph/data/logo.png

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+import os.path
+from io import StringIO, BytesIO
+from typing import BinaryIO
+
+from django.core.files.base import ContentFile
+from django.db import models
+from wagtail.contrib.settings.models import BaseSetting, register_setting
+from wagtail.images.edit_handlers import ImageChooserPanel
+from wagtail.images.models import AbstractRendition
+
+from contrib.opengraph.gen import assemble
+
+
+@register_setting(icon="media")
+class OpenGraphSettings(BaseSetting):
+    class Meta:
+        verbose_name = verbose_name_plural = "paramètres OpenGraph"
+
+    default_bg_image = models.ForeignKey("wagtailimages.Image", null=True, blank=True, on_delete=models.SET_NULL,
+                                         related_name="+")
+
+    panels = [ImageChooserPanel("default_bg_image")]
+
+
+def upload_og_image(instance: "OpenGraphRendition", filename: str) -> str:
+    filename = instance.rendered.field.storage.get_valid_name(filename)
+    return os.path.join("og_images", filename)
+
+
+class OpenGraphRendition(models.Model):
+    key = models.CharField(max_length=256, primary_key=True)
+    rendered = models.ImageField(upload_to=upload_og_image, width_field="width", height_field="height")
+    width = models.IntegerField()
+    height = models.IntegerField()
+
+    def get_object_url(self):
+        return self.rendered.url
+
+    @classmethod
+    def create_rendition(cls, background: BinaryIO, key: str, title: str) -> "OpenGraphRendition":
+        from PIL.Image import open
+
+        try:
+            return cls.objects.get(key=key)
+        except cls.DoesNotExist:
+            with open(background) as bg:
+                rendition = assemble(bg, title)
+            img_io = BytesIO()
+            rendition.convert("RGB").save(img_io, format="JPEG", quality=90)
+            img_content = ContentFile(img_io.getvalue(), f"rendition_{key}.jpg")
+
+            rendition = OpenGraphRendition(key=key, rendered=img_content)
+            rendition.save()
+            return rendition